ContentResolver和MyProvider的使用

这里需要两个demo来进行测试，所以在这里我就直接上代码了。

第一个demo，提供者：

这里就需要配置一下了，因为是四大组件嘛，配置代码是：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.zking.laci.android25_sqllite">

    <application android:allowBackup="true" android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true" android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <provider
            android:authorities="com.zking.laci.android25_sqllite.MyProvider"
            android:name=".MyProvider"
            android:exported="true"
            ></provider>
    </application>

</manifest>

provider的第一个属性是放相当于网址的东西，测试的话，我们就用包名加类名写上去，第二个属性是放我们发送者的类，第三个属性是说明可以被访问。

MainActivity类代码：

package com.zking.laci.android25_sqllite;

import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import com.com.zking.laci.db.DBHelper;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        DBHelper db=new DBHelper(this,"test.db",null,1);
        SQLiteDatabase sqLiteDatabase=db.getWritableDatabase();
        for (int i = 0; i <100 ; i++) {
            sqLiteDatabase.execSQL("insert into login(uname,upass) values('小白"+i+"','"+i+"')");
        }
    }
}

提供者MyProvider类代码：

package com.zking.laci.android25_sqllite;

import android.content.ContentProvider;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;

import com.com.zking.laci.db.DBHelper;

/**
 * Created by Laci on 2017/7/17.
 */

public class MyProvider extends ContentProvider{
    @Override
    public boolean onCreate() {
        return false;
    }

    @Nullable
    @Override
    public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
        DBHelper db=new DBHelper(getContext(),"test.db",null,1);
        SQLiteDatabase sqLiteDatabase=db.getWritableDatabase();
        return sqLiteDatabase.rawQuery("select * from login",null);
    }

    @Nullable
    @Override
    public String getType(@NonNull Uri uri) {
        return null;
    }

    @Nullable
    @Override
    public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
        return null;
    }

    @Override
    public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
        return 0;
    }

    @Override
    public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
        return 0;
    }
}

DBHelper类：

package com.com.zking.laci.db;

import android.content.Context;
import android.database.DatabaseErrorHandler;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

/**
 * Created by Laci on 2017/7/17.
 */

public class DBHelper extends SQLiteOpenHelper{
    public DBHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
        super(context, name, factory, version);
    }

    public DBHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version, DatabaseErrorHandler errorHandler) {
        super(context, name, factory, version, errorHandler);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("create table login(uid integer primary key autoincrement,uname,upass)");

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}

访问者的demo代码：

在这里我就直接在后台测试了，所以我们需要改动的只有一个类

MainActivity类：

package com.zking.laci.android25_shou;

import android.content.ContentResolver;
import android.database.Cursor;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //获得访问者
        ContentResolver cr=getContentResolver();
        //得到Uri
        Uri u=Uri.parse("content://com.zking.laci.android25_sqllite.MyProvider");
        //得到提供者的内容
        Cursor cursor=cr.query(u,null,null,null,null);
        while(cursor.moveToNext()){
            String uname=cursor.getString(cursor.getColumnIndex("uname"));
            Log.i("test",uname);
        }

    }
}

需要注意的是，要选运行提供者的类之后才能运行访问者的类，今天只是简单的说一下怎么去使用，那么现在就结束啦，我们下篇博客再见咯！